It's hard to gauge the popularity of the Western, but for a genre that once dominated the entertainment world, it's seen better days. After its heyday in the 50s and 60s, the Wild West fell on hard times and then disappeared into a chorus of flatulence in The Blazing Saddles. For a while, the superb TV series Deadwood was a worthy standard bearer, but sadly it was cancelled after three seasons. These days, cowboy films are usually greeted with a muted response, even if they are critically acclaimed. Video games set in the Wild West are extremely thin on the ground, which seems odd when one considers how many elements of the genre (such as guns, anti-heroes and the odd damsel in distress) would translate well into the medium. Bearing all this mind, it would seem that Red Dead Redemption, the latest sandbox adventure from Rockstar Games, is riding into pretty uncertain territory. It's impossible to predict how successful it will be. But it certainly deserves to be an unqualified hit.

Red Dead Redemption starts to weave its magic from the moment the player is dropped into its note-perfect Wild West environment. This really shouldn't come as much of a surprise. After all, Rockstar is in a class of its own when it comes to open-world games, and even if the developer can't lay claim to the invention of the genre, it can certainly boast a certain mastery of it. But the achievements of Rockstar San Diego in regards to Red Dead Redemption are all the more impressive given that the world of the Wild West doesn't naturally lend itself to easy coding. It looks and feels like the genuine article in every detail, from the ramshackle, imperfect wooden structures, to the unpredictable movements of a stagecoach as it travels over uneven ground, to the irregular progression of a tumbleweed as it is blown across a street. It may sound strange to remark upon how convincingly real a lasso looks in a video game, but consider what goes into accomplishing this. Then consider how easy it would be to shatter the perceived authenticity of this world, if just one aspect felt out of place.

Not only does the world of Red Dead Redemption look the part, but Rockstar have also filled their Wild West with an entire ecosystem (which includes bears, pumas, snakes, deer and buffalo), a huge array of random encounters – such as stagecoach robbers and escaped convicts – and an immense amount of off-mission content. Red Dead Redemption is practically bursting at the seams with extra activities. Players can hunt animals, skin them and sell their pelts and meat in towns for services and goods. They can choose to ride shotgun on a stagecoach, fending off would-be robbers. They can lasso and break horses for ranchers and take part in cattle drives. They can engage in a spot of bounty hunting or raid forts held by bandits and steal their treasure. If they're feeling lucky, they can sit down for a game of blackjack, liars' dice, Texas hold 'em or five-finger-fillet. The Wild West environment of Red Dead Redemption is an immense technical achievement. The visuals, soundtrack and organic physics combine to suck the player in completely. It's easy to get lost in Red Dead Redemption – and this is true of it before you even start playing through the campaign.

The single-player story is a gritty tale set during the dying days of the Wild West. Players pull on the cowboy boots of John Marston, a former bandit whose attempts at leaving his criminal past behind him have been derailed by the authorities. The newly formed Bureau want to hunt down and capture Marston's former gang, and since their efforts have been unsuccessful, they've asked Marston to do the job for them. Marston is understandably hesitant to do this; while his old compatriots may be homicidal outlaws, there once was a time he considered them family and old loyalties die hard. However, the Bureau aren't really offering Marston a choice – if he refuses or fails to bring his former partners in crime to justice, they will murder his wife and son. In John Marston, Rockstar have created one of their strongest and most compelling characters to date; a relic of the last lawless days of the old west, Marston is an individual who has traded in his ruthless nihilism for grim-faced pragmatism. His face is a mess of unshaven hair and scars, his eyes convey a bleak acceptance of his plight and his dust-choked voice, provided by Rob Wiethoff, is equal parts stoic resignation and barely restrained menace. Marston heads up a colourful cast of drunks, con-men, revolutionaries, villains and long-suffering citizens; the law of the land seems skewed against anyone trying to make and honest living, and only those with total disregard for it seem to have a chance at prosperity – and this includes the Bureau's lawmen.

It's tempting to chalk Red Dead Redemption up as simply the Wild West entry in the Grand Theft Auto franchise. There's the vast environment, the well-drawn characters, the plethora of side-quests, the extra activities, the well-written dialogue and above all, the near-limitless potential for exploration and mayhem once the main story has been completed. However, while the GTA: Wild West tag is useful in explaining Red Dead Redemption as a concept, it does Rockstar's latest offering a disservice. Like every title that rattles off the Rockstar production line, Red Dead Redemption is clearly an ambitious and unique offering. It may share certain gameplay mechanics and environment structure with its GTA stablemates but its overall tone, incredible sense of place and time, and its focus on morality mark it out as a very different animal altogether. This last feature can't be overstated; while the GTA games always tempered the player's capacity for chaos by hurling ever increasing numbers of heavily armed police at them, Red Dead Redemption's moral compass subtly informs nearly every aspect of the single player mode.

As Marston travels across the massive Wild West expanse in search of his former comrades, he is faced with a large array of moral dilemmas – some occur in story missions, some on side-quests and some happen on the fly while the player roams the environment. In each instance, the player has a choice and their fame and reputation will be affected depending on how they decide. Many of the in-game activities grow Marston's reputation, regardless of how the player acts. However, the player's morality is reflected in the game's fame meter which fills towards honour or notoriety depending on how they play. This in turn affects how the NPCs in Marston's environment react to him. Players with positive renown receive perks such as the ability to commandeer NPCs' horses or discounts in the general stores. Those determined to play as desperados shouldn't be surprised when 'wanted' posters of Marston start circulating in every town and every second gunslinger seems to fancy their chances in a quick-draw shoot-out. This sense of moral accountability permeates the game's plot too. Marston's insidious past is an obvious starting point for the entire story, but he's not the only character whose behaviour leads them down a dark road. Morality isn't just a nifty gameplay aspect – it's hard-wired into the single player campaign. In the world of Red Dead Redemption, it seems, no action is without its consequence, and no one gets away clean.

Naturally, Marston's quest calls for a lot of gunplay and Rockstar have provided a brutally satisfying combat system combining the cover-and-fire gameplay from GTA IV, and the Dead-Eye mechanic from Red Dead Revolver. In Dead-Eye, time slows down and allows the player to paint their target with a series of crosses. They then hit the right trigger and Marston fires off a rapid volley which peppers his target with bullets. Perhaps to prevent it from feeling overpowered, the Dead-Eye mechanic needs to be filled with regular kills during shoot-outs. As players progress through the game they will gain access to bigger and better weapons which are available for sale at gunsmiths dotted around the map. As is fitting for an epic Western, Red Dead Redemption contains several impressive action set pieces, involving cannons, Gatling guns and quick draw shoot-outs.

For the most part players will travel on horseback to explore the vast in-game map. The horses are extremely well animated, easy to use and able to pass swiftly over most types of terrain. They behave intuitively, rearing up at the sound of gunfire or the crash of thunder and they resist any attempts to ride them off a sheer drop. Marston can call his horse by whistling; players just press the D-pad and their steed will come running. There are a variety of horses an each offer different advantages, but the longer Marston keeps a horse, the more it will gain in terms of stamina and speed. In keeping with Rockstar's other open-world adventures, Red Dead Redemption offers players a multitude of side-quests and activities to keep them occupied. The side-quests, for the most part, are activated by encounters that are highlighted on the in-game map by a purple question mark. They're mostly optional filler to the main story and pretty familiar fare to anyone who's played a sandbox game from Rockstar before. Red Dead Redemption's main story mode will take players around 15 or so hours to complete if they zoom straight through it, while players who are Achievement (or Trophy) hounds will find it contains upwards of 40 hours of gaming time. And then, of course, there's the multiplayer.

The multiplayer is split into two main modes: free roam and map-based matches. Up to 16 players can take part in map-based games and in free roam mode. There are 5 match types altogether: Free For All Shootout (Deathmatch), Gang Shootout (Team Deathmatch), Hold Your Own (a team-based capture-the-flag match), Grab The Bag (which requires players to fight for a single bag of gold) and Goldrush, an every-man-for-himself match in which all players try to grab saddlebags and drop them at respawning chests. Each match starts with a shoot-out with players employing snapshots and side-rolls to make sure their team wins the contest, or that they're the last person standing. In free-roam mode players can form a posse of up to 8 members. Then the posse leader sets a goal and the newly formed gang can then tackle a variety of targets including bandit-held forts, bounties and hunting wildlife. In keeping with the trend set by Modern Warfare, players earn XP which they can use to unlock new weapons, horses and clothes for their cowboy.

Red Dead Redemption is an awe-inspiring game. The gameplay and structure may be beginning to show their age a little, but the storytelling, characters and world-building are on a par with the best the medium has to offer. It's a sprawling and engrossing experience, epic in scope and size and offering a gigantic amount of playing time. With their latest open-world game, Rockstar have produced nothing less than the finest recreation of the Wild West on a console, and one of the best video games of this year.